It's a cell phone-style game on your brand-new, high-tech DSi.
Bird & Beans is one of the launch games on the DSiWare service, along with Art Style: Aquia, WarioWare: Snapped, and a few others. While it only costs 200 points ($2), it isn't worth any more than that. It is a fun distraction, but there's virtually no content, and it has the air of a cell phone game; something to play on the elevator, but nothing you'd play for more than a few minutes.
The title pretty much sums everything up. You control a bird who has a chameleon-like tongue. Your actions are limited to moving left and right and slurping up beans as they fall from the sky. The bird's tongue extends upward at a diagonal angle, and continues to extend for as long as you hold down the A button. Each consumed bean gives you points. The lower the bean is in the sky when you eat it, the lower the point value. If you get hit by a bean, you die and it's Game Over. If a bean hits the floor, that floor block disappears, limiting your movement. Blocks reappear over time automatically, or by eating a flashing bean (which restores the entire floor).
After beating the high score for the first time you'll unlock Bird & Beans 2, a variation on the original that has the bird blowing leaves around instead of using his tongue. When the leaves hit a bean, the bean explodes into more leaves. The trick here is that you can create a combo by continuously hitting beans with the same leaf pile.
Your high scores are saved, and you can view them from the game's main menu, but that's it. There are probably free Flash games on the Internet that approximate these games. It's best to save your Nintendo Points and wait for something worthwhile.